Best Self Hosted Alternatives to MailerSend

Postal is a fully featured email delivery platform for running your own inbound and outbound mail service. It provides the core components needed to accept, route, and deliver email for applications and domains, similar in scope to hosted transactional email providers.

Key Features

• SMTP service for sending email from applications and services
• Incoming email handling for receiving and processing messages
• Web-based interface for managing organizations, servers, and domains
• Message tracking and log-style visibility into mail delivery
• Designed to operate as a multi-tenant mail platform
• Installation tooling and scripts available to help bootstrap prerequisites

Use Cases

• Self-hosted transactional email platform for web apps and SaaS products
• Centralized mail infrastructure for multiple domains and teams
• Inbound email processing pipelines (for example, support or app workflows)

Limitations and Considerations

• Requires careful DNS and deliverability setup (SPF/DKIM/DMARC) to achieve reliable inbox placement
• Running production email infrastructure typically requires IP reputation management and ongoing monitoring

Postal is well-suited for teams that need control over email sending and receiving infrastructure while retaining a modern management interface. It offers a practical foundation for operating a SendGrid-like mail service on your own servers.

Haraka is an open source, event-driven SMTP server written in Node.js. It is designed for high throughput and concurrency, and is commonly deployed as a filtering MTA or mail submission agent (MSA) via a flexible plugin system.

Key Features

• Modular plugin architecture to customize SMTP behavior and mail processing
• High-performance asynchronous design suitable for thousands of concurrent connections
• Built-in outbound delivery and queueing for authenticated/relayed messages
• Supports common email authentication and policy needs via plugins (for example DKIM and SPF)
• Useful as a filtering layer alongside a separate mail store and IMAP server

Use Cases

• Run a high-throughput SMTP front-end with custom filtering and routing rules
• Deploy an MSA on port 587 with authentication and outbound signing policies
• Add specialized anti-spam and validation logic in front of an existing mail system

Haraka is a strong fit when you want a programmable SMTP server that is easy to extend in JavaScript and integrates with existing mail storage and IMAP solutions. Its plugin ecosystem enables practical customization without modifying the core server.

Hyvor Relay is an open-source, self-hosted Email API designed for developers and organizations that need programmatic email sending with deliverability controls and observability. It combines a REST API backend, Go-based workers and SMTP servers, and a SvelteKit frontend to provide a complete mail delivery platform for transactional and distributional workflows.

Key Features

• RESTful, idempotent Email API that supports HTML/plain text, attachments, custom headers, and multiple recipients.
• Built-in SMTP sending components, delivery retries, greylisting handling, bounce & complaint management, and suppression lists.
• Automated DNS handling (MX/SPF/DKIM) via an integrated DNS server to simplify domain setup and signing.
• Multi-tenant projects with scoped API keys, webhooks for real-time event delivery, and 30-day searchable email logs including SMTP traces.
• Observability integrations with Prometheus metrics and Grafana dashboards, plus health checks and deliverability monitoring.
• Flexible deployment: Docker Compose / Swarm-based self-hosting, plus an enterprise licensing option with commercial support.

Use Cases

• Developers building transactional email delivery (password resets, receipts, notifications) with full control over deliverability and logs.
• Organizations wanting a self-hosted alternative to third-party providers for privacy, auditability, or regulatory reasons.
• Teams that need integrated observability and automation for large-scale sending (queue isolation, health checks, metrics).

Limitations and Considerations

• The project is licensed under AGPL-3.0; organizations that cannot accept AGPL obligations may need the commercial enterprise license option.
• The hosted "Cloud" offering was planned as a separate managed product with initial focus on transactional email; self-hosting remains the primary production path for many users.
• Hyvor Relay does not include built-in newsletter management or advanced marketing/list-management features; it targets email sending and delivery rather than full campaign management.

In summary, Hyvor Relay provides a developer-focused, open-source email sending platform with integrated DNS automation, webhooks, and observability. It is suitable for teams that need a self-hosted, extensible alternative to managed email providers while accepting AGPL licensing or opting for a commercial license.

(relay.hyvor.com)

DragonFly Mail Agent (dma) is a small Mail Transfer Agent (MTA) designed for home and office use. It accepts mail from locally installed Mail User Agents and delivers messages either to local mailboxes or to remote SMTP destinations. Remote delivery includes TLS/SSL support and SMTP authentication.

Key Features

• Lightweight, C-based MTA focused on local submission and outbound delivery
• Local delivery to system mailboxes and forwarding to remote SMTP servers
• TLS/SSL support and SMTP authentication for secure remote delivery
• Does not listen on port 25; intended as a simple MTA rather than a full internet-facing server
• Simple installation and configuration with sendmail-compatible links and basic mail queue tools

Use Cases

• Provide an outbound relay for desktops, servers, or a home network
• Deliver system and application notifications to local mailboxes
• Offer a minimal MTA for small offices or embedded systems where full-featured MTAs are unnecessary

Limitations and Considerations

• Not intended to replace full-featured MTAs; lacks many advanced features such as inbound SMTP on port 25, extensive routing/virtual hosting, and advanced filtering
• Limited scalability for high-volume or enterprise mail infrastructures

DragonFly Mail Agent is a pragmatic, minimal MTA for environments that need simple local delivery and secure remote relay. It is best suited where low resource usage and straightforward configuration are priorities.

Sendmail Open Source is the open-source subset of Proofpoint's Sendmail Sentrion platform, designed for large and complex mail environments. The current Open Source release is Sendmail 8.16.1, distributed as a tar.gz archive with a PGP signature, and signed by the 2025 signing key. OpenDKIM is referenced as part of the Open Source offering.

Key Features

• Open Source subset of Sendmail Sentrion for enterprise-scale environments.
• Release 8.16.1 available on ftp.sendmail.org as a tar.gz archive with a PGP signature; signatures generated with the 2025 signing key.
• Includes OpenDKIM integration (DKIM) to authenticate messages.
• Security and licensing guidance, including CERT contact points and PGP signing keys.

Use Cases

• Deployments in large, complex mail infrastructures needing a durable open-source MTA with long-term manageability (virtualization, consolidation, cloud migration).
• Environments requiring verifiable, signed open-source builds from ftp.sendmail.org for audits and compliance.
• Setups needing DKIM-based mail signing and authentication controls.

Limitations and Considerations

• The Open Source option is a subset of the full Sendmail Sentrion offering; some enterprise features may be unavailable. Consult a specialist to assess fit.

Conclusion

Sendmail Open Source provides an officially supported open-source path for enterprise-style email deployments within the Sendmail Sentrion lineage. It offers a current release (8.16.1) with signed distributions and OpenDKIM support, suited for organizations able to manage an open-source MTA stack.

Exim is a message transfer agent (MTA) for Unix-like systems, originally developed at the University of Cambridge. It handles SMTP email transport and is designed for highly flexible routing and policy-driven control over how mail is accepted, processed, and delivered.

Key Features

• SMTP server and outgoing transport for Internet email delivery
• Highly configurable routing and delivery logic for complex mail flows
• Extensive access control and checks for incoming mail during SMTP transactions
• Can replace sendmail-style MTAs, with a distinct configuration model
• Supports integrations commonly used in mail stacks (for example TLS and SMTP authentication)

Use Cases

• Operating a mail server that accepts and relays inbound/outbound SMTP mail
• Building policy-heavy mail routing for multi-domain or multi-tenant environments
• Providing a configurable MTA component alongside IMAP/POP3 and spam-filtering systems

Limitations and Considerations

• Configuration is powerful but can be complex compared to simpler MTAs
• Security fixes are important; older releases can be obsolete and should be avoided

Exim remains a widely used, flexible MTA for administrators who need fine-grained control over mail routing and inbound SMTP policy. When maintained and kept up to date, it can serve as the core SMTP transport component in a full email infrastructure.

chasquid is an SMTP (email) server designed to send and receive mail like a traditional MTA, with an emphasis on simplicity, secure defaults, and ease of operation. It is aimed primarily at individuals and small groups who want a manageable mail server without excessive complexity.

Key Features

• SMTP server for sending and receiving email (MTA functionality)
• Secure-by-default behavior to avoid harmful misconfiguration (for example, preventing open relays and clear-text authentication)
• Multiple and virtual domains with per-domain users and aliases
• Support for address suffix dropping (user+tag@domain to user@domain)
• Dovecot integration for authentication
• Hooks for integrating greylisting, anti-virus, anti-spam, and DKIM/DMARC tooling
• SPF and MTA-STS checking
• Per-domain tracking of TLS support to prevent downgrade attacks
• Multiple TLS certificates and easy integration with Let's Encrypt
• Monitoring HTTP server with exported variables and tracing for debugging

Use Cases

• Running a small personal or family email server with safer defaults
• Hosting mail for a small organization with multiple domains and aliases
• Replacing heavier MTAs (such as Postfix or Exim) where simpler operation is preferred

Limitations and Considerations

• Not intended to replicate the full breadth of features and ecosystem integrations typical of very large-scale MTAs

chasquid provides a pragmatic SMTP server focused on operational simplicity while maintaining strong security practices. It is a solid fit when you need a traditional MTA with modern security checks and minimal administrative overhead.

OpenSMTPD is an open-source implementation of the server-side SMTP protocol (RFC 5321) originally developed as part of the OpenBSD project. It provides a minimal, security-focused mail transfer agent with a compact configuration model, extensible table backends and a filters API for mail processing.

Key Features

• Implements SMTP and common extensions with an emphasis on correctness and RFC compliance.
• Small, modular C daemon designed with privilege separation and process isolation to reduce attack surface.
• Declarative smtpd.conf with expressive match/action rules and built-in table support (examples in the codebase include passwd, sqlite and ldap table backends).
• Filters API and external filter/queue helpers allow integration of greylisting, DKIM signing, Rspamd, and other processing as separate components.
• Delivery options include maildir and mbox formats, an MDA helper, and LMTP client support for local delivery.
• TLS support via libtls/libressl with compatibility for OpenSSL builds, and per-listener TLS/cipher configuration options.
• Portable distribution and an "extras" set of table/filter modules allow packaging for non-OpenBSD systems while keeping the core minimal.

Use Cases

• Host SMTP for small organizations or single-host mail services that prioritize a small, auditable codebase.
• Deploy as a mail gateway/relay that enforces policy via filters and external scanners (spam, DKIM, greylisting).
• Integrate with system account stores or directory services using table backends (passwd, sqlite, LDAP) for virtual users and lookups.

Limitations and Considerations

• Advanced features such as DKIM signing, comprehensive anti-spam, or virus scanning are typically provided via external filters or proxies rather than baked into the core; administrators must deploy and configure filter components for those functions.
• Historical security advisories (patched in later releases) demonstrate the need to track upstream security fixes and apply updates promptly for exposed versions.
• The project prefers LibreSSL/libtls but supports OpenSSL; TLS behavior and available cipher/protocol features can vary depending on the TLS library used.

OpenSMTPD is a focused, security-oriented MTA that favors clarity and modularity. It is well suited for administrators who want a small, auditable mail server core and to assemble additional functionality via filters and table backends.

Dovel is a lightweight SMTP server written in Go that focuses on simplicity and extensibility. It receives and sends email according to a single JSON configuration file and delegates mailbox/storage actions to user-provided hooks. (pkg.go.dev)

Key Features

• Written in Go with a single config file (defaults to $XDG_CONFIG_DIR/dovel/config.json) for easy setup and portability.
• Receives mail and executes executable hooks named receive-<DOMAIN>, passing the message in mbox format to the hook for custom storage or processing.
• Sends mail using a configured vault/users JSON file and supports per-user DKIM signing for outbound messages.
• TLS support via certificate and private key fields in the config (used for encrypted SMTP on submission ports).
• Listens on standard SMTP ports (25, 587, 465, 2525 configurable) and exposes a simple optional web interface for browsing messages.
• Debug/logging controlled by the DEBUG environment variable for developer troubleshooting. (pkg.go.dev)

Use Cases

• Self-hosted personal or small-team mail handling where incoming messages are processed by custom scripts (hooks) and stored in custom formats.
• Developer workflows that need programmatic delivery of inbound email to local tools, APIs, or archiving scripts.
• Simple transactional mail sender for services that can provide per-user DKIM keys and manage DNS records for deliverability. (pkg.go.dev)

Limitations and Considerations

• No built-in IMAP/POP3 mailbox server functionality; message storage/management is delegated to hooks so external tooling is needed for mailbox access.
• No integrated spam filtering, antivirus, or advanced MTA features (bouncing policies, rate limiting, reputational services) — these must be provided externally.
• Deliverability requires correct DNS/SPF/DKIM/DMARC configuration and operational handling (outbound reputation, PTR records) which are not automated by the server. (pkg.go.dev)

Dovel provides a compact, script-extensible SMTP server implementation intended for users who prefer a minimal, Go-based mail gateway that hands message storage and processing to custom hooks. It is most appropriate where straightforward SMTP receive/send behavior and per-message scripting are sufficient.

Postfix is an SMTP mail transfer agent (MTA) used to send, receive, and route email between mail servers and local delivery services. Originally developed by Wietse Venema as an alternative to Sendmail, it is designed to be fast, secure, and straightforward to administer on Unix-like systems.

Key Features

• SMTP server and mail relay capabilities for inbound and outbound mail flow
• Queue management for reliable delivery and handling of transient failures
• Flexible routing and policy controls (transports, relaying rules, restrictions)
• Pluggable integrations for authentication, filtering, and content scanning via common mail workflows
• Support for modern operational needs such as TLS-encrypted SMTP and extensive logging

Use Cases

• Running an organization’s primary mail transfer agent for SMTP delivery
• Operating a secure outbound relay (smart host) for applications and servers
• Building a mail gateway in front of internal mailboxes with filtering and routing rules

Limitations and Considerations

• Postfix is an MTA, not a full groupware or webmail solution; mailbox access typically requires separate IMAP/POP and webmail components
• Advanced features (spam filtering, DKIM/DMARC, antivirus, mailbox storage) usually rely on integrating additional services

Postfix remains a widely deployed choice for SMTP delivery thanks to its security-focused design and mature operational tooling. It fits both small deployments and high-volume mail infrastructure when combined with appropriate mailbox and filtering components.